JP5593654B2 - Robot joint - Google Patents

Description

The present invention relates to a robot joint.

  In the processing line and assembly line of industrial machines, various robot arms are used for labor saving and automation. On the other hand, in recent years, partner robots and household robots that are familiar to human beings have been actively developed. Rolling bearings are used for the robot joints of these robots, for example, the finger joints of the robots (for example, Patent Document 1).

  In general, when a rolling bearing is used, it is conceivable that the rolling bearing is fixed with an adhesive as an attachment method.

JP 2006-329420 A

  However, when a rolling bearing is fixed to the robot joint using an adhesive, it is known that outgas is generated depending on the ambient temperature and use conditions, which is not preferable. In addition, if a bearing that is completely fixed with an adhesive has a problem, it is difficult to remove the bearing or bearing unit from the arm member, and the entire arm will be replaced, resulting in poor maintenance performance and high cost. was there.

Therefore, an object of the present invention is to provide a robot joint portion that can fix a rolling bearing to an arm member without using an adhesive and has excellent maintenance performance.

The above object is achieved by the following configuration.
(1) A robot joint in which a connecting portion of a swing arm is rotatably supported by a robot joint bearing unit with respect to a base arm in which a shaft member is attached between a pair of connecting plates, and the swing arm is driven by a wire. Part,
A gap is formed between the pair of connecting plates and the connecting portion,
The robot joint bearing unit is provided with two rolling bearings arranged in parallel to swingably and swingably support a swing arm with respect to the shaft member,
A tolerance ring is provided on the outer peripheral side of the rolling bearing,
The swing arm is provided with a notch for attaching the wire,
The notch is formed in a region of 90 ° or more and 270 ° or less with respect to the rotation center of the swing arm,
The tolerance ring is provided across the two rolling bearings,
The notch is disposed within an axial width of the tolerance ring;
In the rolling bearings, shield plates are attached to the grooves on both sides in the axial direction of the outer ring,
Fluorine coating is applied to the shield plate and the groove,
Labyrinth is formed between the straight inner shoulders opposite the tip of the tip and the shield plate of the shield plate,
The robot joint part, wherein the gap of the labyrinth is in a range of 0.05 mm to 0.15 mm .
(2) The robot joint bearing unit includes a sleeve into which the rolling bearing is fitted, and the tolerance ring is provided between the sleeve and the swing arm.
A material having a larger linear expansion coefficient than the material of the inner ring and the outer ring of the rolling bearing is applied to the swing arm, and a material having a larger linear expansion coefficient than the material of the sleeve is applied to the shaft member. The robot joint according to (1), wherein the robot joint is applied.

  According to the robot joint portion bearing unit of the present invention and the robot joint portion including the bearing unit, it is possible to reduce the influence on the environment and the human body without generating outgas as compared with the case where an adhesive is used. In addition, since no special adhesive is used, the cost can be reduced. Further, since the bearing unit can be detached from the swing arm as a single unit, maintenance can be easily performed even when a malfunction occurs.

It is a perspective view which shows the outline of the robot finger carrying the robot joint part bearing unit which concerns on this invention. It is sectional drawing of a robot joint part. It is sectional drawing of a rolling bearing. It is an external appearance perspective view of a tolerance ring.

Hereinafter, an embodiment of a robot finger equipped with a bearing unit according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing an outline of a robot finger equipped with a robot joint bearing unit according to the present invention, FIG. 2A is a sectional view of the robot joint showing an overview of the bearing unit, and FIG. FIG. 3 is a sectional view of a robot joint part cut out including a unit, FIG. 3 is a sectional view of a rolling bearing, and FIG.

  As shown in FIG. 1, the robot finger 1 includes a hollow cylindrical first arm 2, a hollow cylindrical second arm 3 composed of a small diameter portion 3a and a large diameter portion 3b, and a hollow cylindrical shape at one end. A hollow cylindrical third arm 4 having a spherical end, a first joint 5 connecting one end of the first arm 2 and one end of the second arm 3, and the second arm 3 And a second joint portion 6 that connects the end portion and one end portion of the third arm 4, the second arm 3 rotates with respect to the first arm 2, and the third arm 4 with respect to the second arm 3. Is configured to rotate. In the following description, the swinging arm member will be described as the swing arm 20, the arm member supporting the swing arm 20 will be described as the base arm 30, and the joint portion connecting the base arm 30 and the swing arm 20 will be described as the robot joint portion 10. . That is, in the robot finger 1, when focusing on the first joint 5, the first arm 2 corresponds to the base arm 30, the second arm 3 corresponds to the swing arm 20, and the second joint 6 is focused. The second arm 3 corresponds to the base arm 30 and the third arm 4 corresponds to the swing arm 20.

  As shown in FIG. 2, the robot joint portion 10 has a bearing unit 40 mounted in a unit mounting hole 22 formed in a connecting portion 21 on one end side of the swing arm 20. The unit mounting hole 22 is formed in a circular shape in a direction perpendicular to the longitudinal direction of the swing arm 20. In the bearing unit 40, two rolling bearings 43 (hereinafter referred to as “bearings”) are arranged in parallel along the rotation center line P between the shaft member 41 and the sleeve 42. A tolerance ring 44 is provided on the outer periphery and integrated.

  The shaft member 41 is configured as a so-called straight shaft in which a cylindrical shape having a constant outer diameter in the entire extending direction, that is, an outer peripheral surface is not provided with, for example, a flange portion or an annular convex portion. ing. However, predetermined chamfered portions are formed on the outer peripheral surface of the shaft member 41 along the circumferential direction at both ends thereof. Further, the shaft member 41 is configured as a hollow straight shaft having a hollow cylindrical shape inside along the extending direction and having female threads formed at both ends. In addition, although the shaft member 41 is configured as a hollow straight shaft, for example, a configuration may be employed in which a flange portion is provided in a ring and a series on one end side of the outer peripheral surface of the shaft member 41.

  The sleeve 42 is formed in a cylindrical shape whose inside is hollow along the extending direction, and an annular convex portion 42a is provided along the circumferential direction on the inner circumferential surface thereof, and the outer circumferential surface thereof. An annular convex portion 42b is provided along the circumferential direction at both end portions. The annular protrusions 42a and the annular protrusions 42b may be formed continuously or intermittently along the circumferential direction, but are not always necessary, and one or both of them may be omitted. . In this case, the sleeve 42 may be configured in a cylindrical shape having a constant inner diameter or outer diameter over the entire extending direction.

  The material of the shaft member 41 and the sleeve 42 having such a configuration is not particularly limited, and any material can be applied. However, in the present embodiment, the material of the shaft member 41 is the sleeve 42. A material having a larger linear expansion coefficient than the material is used. For example, SUS303 steel (austenitic stainless steel) according to JIS standard is applied as the material of the shaft member 41, and manganese (Mn), lead (Pb) and tellurium (Te) are used as the material of the sleeve 42 as SUS403F steel according to JIS standard. (DHS-1: ferritic stainless steel) to which is added is applied.

  As shown in FIG. 3, the bearing 43 includes an outer ring 43 a and an inner ring 43 b that are opposed to each other so as to be relatively rotatable, and a plurality of balls 43 c that are rotatably incorporated between the outer ring 43 a and the inner ring 43 b. It is a deep groove ball bearing provided with the holder | retainer 43d which hold | maintains the some ball | bowl 43c rotatably by predetermined spacing in the circumferential direction.

Further, mounting grooves 43e are provided at both axial ends of the outer ring 43a, and an annular shield plate 43f that forms a labyrinth 43g between the inner ring 43b and the mounting groove 43e is mounted. These two bearings 43 are filled with a predetermined amount of lubricant. The lubricant is a mineral oil-based grease or a synthetic oil-based grease (for example, lithium-based, urea-based, etc.). For high-temperature environment applications, such as fluorine-based grease or fluorine-based oil, fluorine resin, or MoS ₂ Solid lubricant. However, the solid lubricant is directly applied to the raceway grooves of the balls 43c, the outer ring 43a, and the inner ring 43b. In this bearing 43, for example, foreign matter (for example, dust) enters from the outside of the bearing 43 or lubricant (for example, grease or lubricating oil) leaks from the inside of the bearing 43 by the shield plate 43f and the labyrinth 43g. Etc. are prevented.

  Here, the outer surfaces of the mounting groove 43e and the shield plate 43f are preferably coated with fluorine, and the gap between the labyrinth 43g is preferably less than 0.5 mm, and more preferably 0.05 mm or less. The fluorine coating and the labyrinth 43g are effective in water penetration resistance and lubricant leakage.

  As an example, a crown-shaped cage is applied to the cage 43d, and the two cages 43d are incorporated in the bearings 43 with their openings facing each other, and between the outer ring 43a and the inner ring 43b. It is rotating. The two retainers 43d may be incorporated in the bearing 43 with their openings directed in the same direction, or may be incorporated in the bearing 43 with the other side (the closed side opposite to the opening) facing each other. Moreover, although the crown type is applied as the retainer 43d, various types such as a wave retainer, a cage retainer, and a combined retainer can be applied.

  In the bearing 43 having such a configuration, the material is not particularly limited, and any material can be applied. However, in the present embodiment, as the material of the swing arm 20, the outer ring 43a and the inner ring of the bearing 43 are used. A material having a larger linear expansion coefficient than the material of 43b is applied.

  Each bearing 43 is given a predetermined preload, and such a preload can be given by the following method. For example, the annular protrusion 42 a is interposed between the outer rings 43 a of the two bearings 43, and the outer rings 43 a are press-fitted and fixed to the inner peripheral surface of the sleeve 42. Then, a preload is applied to the inner ring 43b of one side bearing 43 (the left side bearing in FIG. 2 (b)) in one direction (right direction in the figure) with respect to the axial direction (left and right direction in the figure). The inner ring 43b of the bearing 43 is press-fitted and fixed to the shaft member 41. Similarly, a preload is applied to the inner ring 43b of the other bearing 43 (the right bearing in FIG. 2B) in the other direction (leftward in the figure) in the axial direction (leftward in the figure). In this state, the inner ring 43 b of the bearing 43 is press-fitted and fixed to the shaft member 41. As a result, a predetermined preload can be applied to the two bearings 43. For example, the swing arm 20 can be traced on the hard disk quickly and smoothly without rattling when the swing arm 20 swings slightly.

  In the bearing unit 40, a tolerance ring 44 is provided on the outer periphery of the sleeve 42, and the bearing unit 40 is fixed to the unit mounting hole 22 of the swing arm 20 by the tolerance ring 44. The tolerance ring 44 is a member that is interposed between two members and positions and fixes these members to each other. As shown in FIG. 4, for example, the tolerance ring 44 is annular with an elastic material (spring material). The outer peripheral surface is provided with a plurality of convex portions 44a at equal intervals along the circumferential direction (referred to as an outer diameter type with respect to the inner diameter type described later). The portion 44 a acts as a spring having an elastic force biased in the radial direction of the tolerance ring 44.

  In this case, as an example, in the state where the bearing unit 40 is fixed to the swing arm 20, the tolerance ring 44 has an outer diameter (a diameter of a virtual circle in which the maximum height portion of the convex portion 44 a is continuous) of the unit mounting hole 22. It is comprised so that it may become substantially the same as the diameter of. For this reason, in the state before the bearing unit 40 is fixed to the swing arm 20 (the state shown in FIG. 4), the tolerance ring 44 has an outer diameter (the diameter of a virtual circle that continues the maximum height portion of the convex portion 44a). The diameter is slightly larger than the diameter of the unit mounting hole 22. Further, as an example, the tolerance ring 44 is configured such that the width thereof is substantially the same as the distance between the annular convex portions 42 b provided at both ends of the outer peripheral surface of the sleeve 42.

  In the configuration shown in FIG. 4, the tolerance ring 44 is configured to have an annular shape, but may be configured to have, for example, a C shape in which a part of the annular shape is cut out. Further, the tolerance ring 44 may have a divided configuration. For example, the tolerance ring 44 may be configured to have a substantially annular shape by combining two tolerance rings 44 that form a semicircle obtained by dividing a circle into two. Here, the shape, size, number, and the like of the convex portion 44a of the tolerance ring 44 are arbitrarily set according to, for example, the size and shape of the tolerance ring 44 and the distance between the sleeve 42 and the unit mounting hole 22. Therefore, there is no particular limitation here.

  By interposing the tolerance ring 44 between the sleeve 42 and the unit mounting hole 22 of the connecting portion 21, the bearing unit 40 and the swing arm 20 can be easily and reliably connected by the elastic force and frictional force of the tolerance ring 44. Can be fixed. As an example of a specific method of fixing the bearing unit 40 and the swing arm 20 using the tolerance ring 44, first, the unit mounting hole 22 of the connecting portion 21 is in contact with the convex portion 44a of the tolerance ring 44. Then, the swing arm 20 is inserted into the bearing unit 40 with the tolerance ring 44 mounted thereon. At this time, the convex portion 44a of the tolerance ring 44 is elastically deformed inward in the radial direction, and the outer diameter of the tolerance ring 44 is slightly reduced.

  When the swing arm 20 is positioned so that both axial end surfaces of the connecting portion 21 are substantially flush with both axial end surfaces of the sleeve 42, the convex portion 44a of the tolerance ring 44 is elastically outward in the radial direction. Deform (deform to return to the original state). The bearing unit 40 and the swing arm 20 are caused by the elastic force generated when the convex portion 44a is urged outward in the radial direction and the frictional force generated between the convex portion 44a and the unit mounting hole 22. Can be fixed.

  The sleeve 42 and the swing arm 20 may be fixed by attaching (interior) the tolerance ring 44 to the connecting portion 21 side of the swing arm 20 and inserting the sleeve 42 into the swing arm 20. In this case, for example, the tolerance ring 44 may have a configuration (inner diameter type) in which a convex portion 44a similar to the above is provided on the inner peripheral surface.

  Subsequently, the connecting portion 21 of the swing arm 20 in which the bearing unit 40 is attached is interposed between a pair of connecting plates 35 formed at one end of the base arm 30, and the shaft member 41 of the bearing unit 40 is connected from the outside of the connecting plate 35. Tighten the connecting screw 14. On the outer peripheral surface of the connecting portion 21 of the swing arm 20, a notch 23 is formed in an area of 90 ° or more and 270 ° or less with respect to the rotation center line P, one end is connected to the driving force transmission device 15 and the other end is not. A wire 16 connected to the illustrated reaction force member is wound around the notch 23.

  The reaction force member is an elastic member such as a spring, for example, and the bearing unit 40 is moved in the opposite direction to the direction in which the swing arm 20 is rotated by the tensile force of the wire 16 (directions indicated by symbols Y1 and Y2 in FIG. 1). A force is generated to rotate the lens.

  When the robot finger 1 configured as described above applies a tensile force to the wire 16 a by driving the driving force transmission device 15, the sleeves 42 supported by the two ball bearings 43 of the bearing unit 40 smoothly rotate around the shaft member 41. Since it moves, the 2nd arm 3 rotates to a predetermined angle in the reverse direction with respect to the Y1 direction shown in FIG. 1 with high precision. Further, when a tensile force is applied to the wire 16b by driving the driving force transmission device 15, the sleeves 42 supported by the two ball bearings 43 of the bearing unit 40 smoothly rotate around the shaft member 41. The arm 4 rotates with high accuracy up to a predetermined angle in the opposite direction to the Y2 direction shown in FIG. When the drive of the driving force transmission device 15 is released and the wire 16a is returned by a predetermined amount, the second arm 3 is rotated to a predetermined angle in the Y1 direction by the force of the reaction member. Furthermore, when the drive of the driving force transmission device 15 is released and the wire 16b is returned by a predetermined amount, the third arm 4 is rotated to a predetermined angle in the Y2 direction by the force of the reaction force member.

  As described above, according to the present embodiment, by using the tolerance ring 44, it is possible to reduce the cost because a special adhesive is not used, and outgas compared to the case where an adhesive is used. It is possible to reduce the impact on the environment and human body. Further, the swing arm 20 and the bearing unit 40 can be removed from the base arm 30 by removing the connecting screw 14, and the bearing unit 40 is axially resisted by the frictional force between the tolerance ring 44 and the unit mounting hole 22. The bearing unit 40 can be removed from the swing arm 20 by pressing. Therefore, maintenance can be easily performed even when a problem occurs.

  Here, the robot finger 1 may be used in a high temperature condition. However, in the present embodiment, as described above, the material of the swing arm 20 is greater than the material of the outer ring 43a and the material of the inner ring 43b of the bearing 43. Since a material having a large linear expansion coefficient is applied, when the swing arm 20 and the bearing 43 are thermally expanded, the swing arm 20 is expanded more than the bearing 43. As a result, the swing arm 20 moves relatively minutely in a direction away from the bearing 43 by a distance corresponding to the difference between the expansion amounts of the two. In other words, the distance between the unit mounting hole 22 of the swing arm 20 and the outer peripheral surface of the sleeve 42 to which the bearing 43 is fixed slightly expands by a distance corresponding to the difference in expansion amount. become.

  In the present embodiment, as described above, a material having a larger linear expansion coefficient than the material of the sleeve 42 is applied as the material of the shaft member 41, so that the shaft member 41 and the sleeve 42 are thermally expanded. In this case, the shaft member 41 expands larger than the sleeve 42. As a result, the distance between the outer peripheral surface of the shaft member 41 and the inner peripheral surface of the sleeve 42 is reduced by a distance corresponding to the difference in expansion amount between the shaft member 41 and the sleeve 42.

  For this reason, as the temperature of the robot finger 1 rises, the swing arm 20 and the bearing 43 thermally expand, and the fixing force of the tolerance ring 44 (for example, the elastic force that the tolerance ring 44 presses the sleeve 42 against the bearing 43). Even when the shaft member 41 and the sleeve 42 are smaller, the shaft member 41 and the sleeve 42 are thermally expanded, and the distance between the outer peripheral surface of the shaft member 41 and the inner peripheral surface of the sleeve 42 is the amount of expansion of the shaft member 41 and the sleeve 42. By reducing the distance corresponding to the difference, the radial gap inside the bearing 43 interposed therebetween can be reduced.

  As a result, a decrease in the preload applied to the bearing 43 from the tolerance ring 44 via the sleeve 42 is suppressed, and the rigidity of the bearing 43 is increased, whereby the rigidity of the bearing unit 40 itself can be increased. . Thereby, even when the temperature of the robot finger 1 rises, the rigidity of the bearing unit 40 can be maintained while being increased.

  Further, according to the present embodiment, the labyrinth 43g is formed between the shield plate 43f of the bearing 43 and the inner ring 43b, so that the rotational torque of the bearing 43 can be reduced. Further, when the shield plate 43f is contacted and brought into contact with the inner ring 43b, not only the rotational torque increases, but also the rotational torque fluctuates as the seal torque is added, and accurate position information cannot be grasped at the robot joint. Although accurate control cannot be performed, in the present embodiment, the position of the swing arm 20 can be accurately controlled by forming the labyrinth 43g.

<Example>
Next, the lubricating oil leakage and water penetration resistance test using the bearing unit of the present invention will be described.
As bearing units, two deep groove ball bearings (bearing name: SMR85 (made of stainless steel)) with an inner diameter of 5 mm, an outer diameter of 8 mm, and a width of 2.5 mm are arranged in parallel, and stainless steel shield plates are attached to both ends of the outer ring of each bearing. And configured. The bearing units thus configured were subjected to measurements in Examples 1 to 8 in Table 1 by changing the presence or absence of fluorine coating on the shield plate, the presence or absence of fluorine coating on the mounting groove, and the labyrinth. The measurement was carried out by immersing the four bearing units in 3000 ml of DI water swung with ultrasonic waves having a frequency of 100 kHz under an ambient temperature of 25 ° C. for 3 minutes. The lubricant leakage was measured. In Table 1, the labyrinth minimum indicates that the labyrinth gap T is 0 <T ≦ 0.05 mm, the small labyrinth indicates that the labyrinth gap T is 0.05 <T <0.5 mm, and the large labyrinth is the labyrinth. The gap T indicates 0.5 mm ≦ T <1.0 mm.

The measurement results are also shown in Table 1.
In the case of lubricant leakage, ◎ indicates a state where the lubricant does not leak, ○ indicates a state where the lubricant oozes out from the bearing but does not affect the unit life, and × indicates a state where the lubricant leaks and affects the unit life. . Further, in the water infiltration property, ◎ indicates a state where moisture in the air does not enter, ○ indicates a state where moisture in the air enters but does not affect the unit life, and x indicates a state where moisture enters.
When Examples 1, 3, 5, and 7 and Examples 2, 4, 6, and 8 are compared, it can be seen that water penetration is effective by setting the labyrinth gap T to T <0.5 mm. In addition, comparing Examples 1 and 5, Examples 2 and 6, Examples 3 and 7, and Examples 4 and 8, the shield plate is coated with fluorine, which is effective for both lubricating oil leakage and water penetration. I understand that there is. Further, comparing Examples 1 and 3, Examples 2 and 4, Examples 5 and 7, and Examples 6 and 8, it can be seen that lubricating oil leakage is effective by coating the mounting grooves with fluorine.

  Subsequently, water penetration was measured for the relationship between the presence or absence of fluorine coating on the shield plate and the labyrinth gap. Note that the mounting groove is not subjected to fluorine coating. In the measurement, the labyrinth gap T is set to 1 mm, 0.5 mm, 0 for the bearing unit with the fluorine coating on the shield plate and the bearing unit without the fluorine coating under the same conditions as the above-described lubricant leakage and water penetration resistance tests. Measurement was performed in 5 stages of 15 mm, 0.1 mm, and 0.05 mm. The measurement results are shown in Table 2.

  From this result, it can be seen that fluorine coating on the shield plate greatly affects the water penetration. On the other hand, it was confirmed that by setting the labyrinth gap T to 0.05 mm or less, the bearing can be kept in a state where moisture in the air does not enter regardless of the presence or absence of the fluorine coating on the shield plate.

In addition, the bearing unit and robot joint part of each said embodiment are not limited to what was illustrated to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in the bearing unit of the present embodiment, the sleeve 42 in which the bearing 43 is fitted is provided and the tolerance ring 44 is provided on the outer periphery of the sleeve 42. However, the sleeve 42 is not necessarily provided, and the tolerance is provided on the outer periphery of the bearing 43. A ring 44 may be provided. Thereby, rigidity can be made high.
Moreover, although the deep groove ball bearing was illustrated as the bearing 43, not only this but arbitrary bearings, such as an angular ball bearing, can be selected.

1 Robot finger 2 First arm (base arm)
3 Second arm (swing arm, base arm)
4 Third arm (swing arm)
5 First joint (robot joint)
6 Second joint (robot joint)
DESCRIPTION OF SYMBOLS 10 Robot joint part 16, 16a, 16b Wire 20 Swing arm 23 Notch 30 Base arm 40 Bearing unit (Bearing unit for robot joint parts)
41 Shaft member 42 Sleeve 43 Bearing (rolling bearing)
43a Outer ring 43b Inner ring 43e Mounting groove (groove)
43f Shield plate 43g Labyrinth 44 Tolerance ring

Claims (2)

With respect to a base arm in which a shaft member is attached between a pair of connecting plates, the connecting portion of the swing arm is rotatably supported by the robot joint bearing unit, and the swing arm is a robot joint portion driven by a wire. And
A gap is formed between the pair of connecting plates and the connecting portion,
The robot joint bearing unit is provided with two rolling bearings arranged in parallel to swingably and swingably support a swing arm with respect to the shaft member ,
A tolerance ring is provided on the outer peripheral side of the rolling bearing,
The swing arm is provided with a notch for attaching the wire,
The notch is formed in a region of 90 ° or more and 270 ° or less with respect to the rotation center of the swing arm,
The tolerance ring is provided across the two rolling bearings,
The notch is disposed within an axial width of the tolerance ring;
In the rolling bearings, shield plates are attached to the grooves on both sides in the axial direction of the outer ring,
Fluorine coating is applied to the shield plate and the groove,
Labyrinth is formed between the straight inner shoulders opposite the tip of the tip and the shield plate of the shield plate,
The robot joint part, wherein the gap of the labyrinth is in a range of 0.05 mm to 0.15 mm . Before SL robot joint bearing unit comprises a sleeve fitted into the rolling bearing, the tolerance ring is provided between the swing arm and the sleeve,
A material having a larger linear expansion coefficient than the material of the inner ring and the outer ring of the rolling bearing is applied to the swing arm, and a material having a larger linear expansion coefficient than the material of the sleeve is applied to the shaft member. The robot joint according to claim 1, wherein the robot joint is applied.

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